Process for multiple bending of rods and a bending machine for carrying out this process

ABSTRACT

The multiple bending of rods or other elongated elements into loops in which a rod (or rods) is supported on an abutment and is bent by means of a bending tool which is guided on a circular path around a bolt which determines the bending radius. The rod (or rods) which is to be bent is held by a clamping element which is fixed in relation to the rod (or rods) at least before the individual bends whereby before each individual bend a straight line distance between the bending tool of the bending machine and the clamping element is reduced, by means of a drive, by the length of the loop side piece required for the next single bend.

United States Patent 1191 Peddinghaus et al.

PROCESS FOR MULTIPLE BENDING OF RODS AND A BENDING MACHINE FOR CARRYING OUT THIS PROCESS Inventors: Paul Carl Peddinghaus, 5820 Gevelsberg; Carl Ullrich Peddinghaus, Obere Lichtenplatzer Strasse 276, 5600 Wuppertal-Barmen, both of Germany Filed: Aug. 17, 1971 Appl. No.: 172,540

US. Cl 72/306, 72/10, 72/217, 72/294, 72/DIG; 22

Int. Cl ..z B2ld 11/04 Field of Search 72/217, 388, 7, 10, 11, 72/30, 294, 297, 301, 306, 307, DlG. 4, DIG.

References Cited UNITED STATES PATENTS Ritter 72/7 [4 1 Apr. 16, 1974 2,871,909 2/1959 Bower 72/321 3,438,237 4/1969 Sisler 72/217 FOREIGN PATENTS OR APPLICATIONS 841,206 7/1960 Great Britain 72/294 542,855 l/l932 Germany 72/217 Primary Examiner-Charles W. Lanham Assistant Examiner-M. J. Keenan Attorney, Agent, or Firm-Holman & Stern [5 7] ABSTRACT The multiple bending of rods or other elongated elements into loops in which a rod (or rods) is supported on an abutment and is bent by means of a bending tool which is guided on a circular path around a bolt which determines the bending radius. The rod (or rods) which is to be bent is held by a clamping element which is fixed in relation to the rod (or rods) at least before the individual bends whereby before each individual bend a straight line distance between the bending tool of the bending machine and the clamping element is reduced, by means of a drive, by the length of the loop side piece required for the next single bend.

19 Claims, 7 Drawing Figures mmmm 16' m4 sum 1 of 3 3.803893 PATENTEIJAPR 18 m4 SHEET 2 0F 3 PATENTEDAPRIBIBM 3803893 SHEET 3 BF 3 FIG.7

+ lllvlllillllllllllll lll PROCESS FOR MULTIPLE BENDING OF RODS AND A BENDING MACHINE FOR CARRYING OUT TI-IIS PROCESS BACKGROUND OF THE INVENTION The invention relates to a process for the multiple bending of rods, or other elongated elements, and more particularly but not exclusively of ferro-concrete rods into reinforcing loops, whereby the rod which is supported on an abutment is bent by means of a bending tool which is guided on a circular path around a central bolt which determines the bending radius. Moreover, the invention also relates to a bending machine for carrying out this process. 1

PRIOR ART In a known manner the rods are first cut into predetermined lengths which are required for a loop. These rod lengths are then fed into the bending machine and with the increase of the individual bends are gradually pushed forwards until the last bend has been effected. The work of the gradual increase in bends is both expensive and gives rise to mistakes. The cutting to size of the rod lengths is carried out on a cutting and measuring truck whereas pressure rollers are sometimes used to feed the rods to the bending machine. With this arrangement, however, a certain slipping in the direction of the axis of the rod as well as in the direction of rotation of the rod cannot be avoided so that its use is limited. For this reason only so many bars as can be safely handled manually and fed in are usually processed with the bending machines at the same time.

OBJECTS AND SUMMARY OF THE INVENTION One object of the invention is to provide a process for the multiple bending of rods in an improved form.

In accordance with one aspect of the invention, there is provided a process for the multiple bending of rods or other elongated elements into loops, in which a rod (or rods) which is supported on an abutment is bent by means of a bending tool which is guided on a circular path around a bolt which determines the bending radius, characterized in that the rod (or rods) to be bent is held by a clamping element which is fixed in relation to the rod (or rods) at least before the individual bends, whereby before each individual bend the straight-line distance between the bending tool and the clamping element is reduced, by means of a drive, by the length of the loop side-piece required for the next single bend.

The aforesaid drive can be provided with a switching off device controlled by a signal which responds to adjustable values corresponding to said distance, whereby the drive is switched on again automatically after each individual bend. A further advantage is that the drive can be switched around after the last bend of a loop and then left switched on until the distance for taking in the next rod or rods is achieved between the bending tools and the clamping element. In this way not only is the workconnected with pushing the rod or rods forwards eliminated but, in addition, the adjusting mistakes which can occur during this work are prevented. The individual distance values only need to be adjusted once for every bending programme. In conformity with this, the adjustment values are entered before each individual bend. This suggestion does, in particular, make it possible to use a sequence programme, whereby a programmer feeds in the proposed sequence of equal or unequal side-piece lengths. After a programme such as this has been switched on, the whole process of the gradual decreasing of the distance carries on automatically.

in order to enable higher feed speeds to be achieved it is advantageous if a braking force is exerted on the moving part of the system in the last part of the distance between the bending tools and the clamping element.

In a particularly advantageous construction, in the invention described in the introduction, a rod is grasped either individually or several rods at a time at one end of the bending tool of a first bending machine, with the bending tool acting as a clamping element, the rod is then bent and held in a clamped position so that the first bending machine can then be worked in the longitudinal direction of the rod. Thereupon, a second bending machine which is arranged in the direction of travel behind the first bending machine and which can be operated in the same direction grasps the rod at the end, on the first end, and then holds it in a clamped position. After the intervals of both the bending machines have gradually decreased by the amounts corresponding to the side-piece lengths of the bending angle, the following bends of a loop can then be produced. Here too the rod is best out first along its whole length. Above all one can straighten several rods as they lie close together on a horizontal bearing bed before they are grasped by the first bending machine and they can then be processed on both the bending machines on which the bending tools are guided during this time on vertical circular paths. Naturally several bends can be carried out on each of the two bending machines, with the other bending machine standing in a clamping position.

A further object of the invention is to provide a bending machine in an improved form.

In accordance with a further aspect of the invention there is provided a bending machine for carrying out the process as which a slide is provided in that between the bending tools of the bending machine and the clamping element which is fixed in relation to the rod (or rods), and'the drive for the movable part of the system which comprises the bending tools of the bending machine and a fixed position which is fixed in relation to the rod (or rods), along stretches which can be preadjusted, acts on the moving part, is switched off for the duration of the bending operation and is switched on again by a signal triggered by the bending machine after its bending tools have returned to their starting position.

For this,'it is advantageous to use a sequence programme control for the switching on of the drive, which can be pre-set, in its total period with, said control having the function of switching on the drive for the next length of the loop side-piece in conformity with the return of the bending tools of the bending plate. In this way, the pre-set values of the lengths of the side-pieces of the loops will be entered in their prescribed sequence one after the otherfollowing each bend.

In such a bending machine it is advantageous to construct the part which is fixed in relation to the rod or rods as a bending tool of a second bending machine which holds the rod or loop section in a clamped position. In this way both bending machines can be worked on a common rail for the sake of simplicity.

For the selection of the drive between the bending machine and the part which is fixed in relation to the rod or rods, it is essential that it can be controlled easily. An amazingly good result was achieved with a drive in the form of a hydraulic working cylinder fitted between the movable part and a point fixed in relation to the system and which was acted upon by a hydraulic fluid of constant viscosity and pressure which was kept constant for periods which could be pre-set. If one is careful to ensure a sufficiently large pressure reserve, and the hydraulic fluid is kept at a uniform temperature, this drive can be operated exclusively according to its loading period, in order to bring about the desired decreases in the intervals. This is achieved with a precise time advance by which a loading valve is switched into its opening or closing position, with a precision of only a few parts per thousand. The hydraulic cylinder is constructed to advantage to be loadable on both sides so that at the end of a bending programme it can return to its starting position. Together with a time meter and a sequence programme control one arrives at a fully automatically operating installation.

In a different construction of this invention, one can develop the movable part of the system which consists of the part which is fixed in relation to the rod or rods and the bending tools of the bending machine with an impulse generator which rotates along its path, of which the impulses are added up on a meter which can be adjusted to a number of inpulses which can be preset and when this number of impulses is reached, a switch is actuated for cutting off the drive. The rotating impulse generator can be driven by a shaft which rotates in a specific relationship to the interval reduction. In the simplest form, this shaft carries a wheel which rotates therewith. The use of a sequence programme control also makes it possible in this form of construction to carry out the individual feeds so that they automatically follow each other and are also in the prescribed size.

A further possibility of the adjustment to side-piece lengths subject to bending exists in the fact that along the slide between the bending tools or the bending machine and the point which is fixed in relation to the rod or rods in their distance from each other, inpulse producing devices are arranged which can be adjusted to different values and which cut off the drive switch. SUch impulse producing devices can be constructed in many different ways. They can, for instance, be comprised of switch contacts actuated by a switch finger on the movable part of the system and thus release an impulse. Optical signal devices which work together with photo-cells can also be used.

In a particularly advantage embodiment of the invention, the slide is constructed as a moving electric field defining a linear motor with the movable part of the system and which is switched on until a decrease in distance corresponding to a side-piece length of a loop is reached. In this type of drive, the elements which are otherwise needed to change, for example, a rotary motion into a straight-line movement are not required. For the transmission of energy, it is of particular advantage if the rod or rods to be pushed forwards themselves become part of the movable part of the linear motor.

In the most preferred embodiment of this variation of the invention, the moving field consists of a plurality of sections corresponding can be individually excited, of which the one which to a pre-given length of a sidepiece of a loop can be excited by means of the current being switched on by a single bend. These sections can be easily pre-adjusted by means of adjusting switches, while a sequence programme control takes .over the process of switching on to the next loop side-piece lengths after the bending tools of the bending machine have returned to their starting position.

If two bending machines are used, there is the added advantage of a considerable increase in the production of the machine. The rails which serve as a slide between the two bending machines make possible an exact alignment of the two machines in relation to the rods. It is useful to fix a rod cutter at the point at which the rods pass into the bending machine which is at the rear in the direction of travel.

In order to carry out the particularly advantageous process of bending several rods at the same time, the bolts for the bending radius and the bending tools are arranged between two vertically rotating discs, of which one disc serves to support and the other disc to guide as well as being detachable, whereby the width of the bearing bed corresponds to the'distance of both discs. When the bends which are made at the same time to several rods by means of such a machine have been carried out, only one disc is released so that the completed bends can be taken off the central bolt or bending tool. This operation can be further mechanized by the disc which carries the bolt and the bending tool being fitted with a pushing device, with the bolt and the bending tool being constructed so that they can be led back and by taking-over fingers engaging in the loops which are to be lifted off, after the guide disc has been released, and transporting them away.

A further improvement is that the bending installation can be provided with a range of action for the bending machines which is constructed with measuring stops. These measuring stops can be made adjustable and can therefore be used on the one hand as a limiting means for the whole length of the rod to be bent and on the other hand at the gradual approach in the bending machines they can pre-set the required bending angle side-piece lengths. The stops can be provided in a known way with switches whereby the corresponding movement cycles of the machines are released.

FOr cutting the rods in precise total lengths, it is advantageous not to let the relatively large-sized first bending machine undertake the precision adjustment but to provide a change of position of the rod cutter for this purpose. However, in order not to have to make the range of adjustment for the rod cutter too large one can provide several uniformly distanced stop sizes for the first bending machine, whereby the rod cutter has then only got to be made adjustable in a longitudinal direction in the area between two stop sizes.

The invention will now be more particularly described with reference to the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of one embodiment of a bending machine according to the present invention,

FIG. 2 illustrates an arrangement of a known bending tool,

FIG. 3 is an exploded view showing the rods to be bent and the bending tools,

FIG. 4 is a front view of a bending tool,

DETAILED DESCRIPTION OF THE I EMBODIMENTS Referring now to FIG. 1 there is shown therein a bearing bed 1 from front side 2 of which, rails 3 extend outwardly for receiving a first bending machine 4 and a second bending machine 15. Adjustable stops .6 shown schematically can also be recognized along the action range. The second bending machine 5 carries in.

a rearwardly directed extension a rod cutter 7, which can be displaced in the direction of double arrow 8. For this purpose, it is fitted in a suitable manner in an arm 9 of the bending machine 5, with the arm extending towards the rear. The rod cutter can, of course, also be fitted on the end of the bearing bed 1 since the bending machine 5 can then be taken as far as to in front of the front side 2 of the bearing bed 1.

A known arrangement of bending tools is shown in FIG. 2. A rod 10 which is to be bent is supported on an abutment bolt 11. The rod 10 is bent by means of an actual bending tool 13 around a central bolt 14 which predetermines the bendingradius. Each machine 4 and 5 is provided with the arrangement of tools illustrated in FIG. 2.

Referring to FIG. 3, an embodiment is shown in which the bending tools 13 are guided in vertical circular paths around the central bolts 14. For this purpose, the bolts and tools are arranged on both sides between vertically rotating discs 15 and 16. The discs 16 can be released so that the completed loops can be removed in the manner already mentioned. The bearing bed 1 in this embodiment is covered along its whole width with the rods 10 which are to be bent. Sideholding-bolts 17, of which only the front one is indicated by a reference numeral, only need to exert small aligning and holding forces because the; rods 10 are all supported by the bearing bed 1. The transverse distance of the bolts 17 is selected in such a way thatthe same width is produced as exists between the discs 15 and 16. In this way all the rods 10 can be-fed into the bending machines at the same time and can be bent at the same time.

FIGS. Sa-Sb show a sequence of several bends and FIG. 5a shows the rod which has not yetbeen bent, while FIG. 5b shows the rod after the first bend made by the first bending machine, in which it is held in a clamped position. The rod in FIG. 50 has been bent at its opposite end by the second bending machine. This bend is followed on the same machine, after the interval has been reduced by the necessary length for the side-piece, by a further bend of 90, so that rod then has the appearance which is shown in FIG. 5d. A further bend leads to the shape of the rod illustrated in FIG. 5e. In this state it is held by the second bending machine, while the first machine carries out a further bend, so that the rod takes on the shape shown in FIG. 5f. At this stage only one more bend is needed to arrive at the loop shown in FIG. 53 which closes itself with two side-pieces.

Referring now to FIG. 6 there is shown a bending machine 101 together with a clamping element 103 which is fixed in position in relation to a rod or rods 102 to be bent. The clamping element is, in turn, able to be operated in relation to the bending machine 101 by means of wheels 104 on a rail 105. The clamping element is constructed specially as a clamping carriage which holds the rods 102 by means of a clamping jaw 106.

A cylinder 107 which is fixed in position has its piston 108 connected with a piston rod which in turn is connected on the clamping carriage. The cylinder 107 can be loaded on both sides of its piston 108 and for this purpose is provided with inflow and outflow pipes 109 and 1 10, which are controlled by a reversing valve 1 1 1, by choice, and the valve is in communication with a hydraulic fluid held in a unit 112 and fluid is directed to the valve by. means of a pressure pump at a constant pressure value and which is thermostatically regulated so that a viscosity which always remains the same is realized. v

A delivery pipe 113 leads from the unit 1 12 to the reversing valve 111 through a pilot valve 114. This pilot valve 114 is switched on by a time meter 115 for predetermined periods which are measured in such a way that a specific volume of the hydraulic fluid enters through the pipe into the cylinder 107, with the volume in turn corresponding to a specific change in -interval. After this time is up, the valve 114 switches over in such a way that the hydraulic fluid flows back through pipe 116 into the unit 112. The time meter is, at this time, still under the influence of a sequence programme control 117 by means of which the individual time values of the time meter 115 can be set in sequence and also by means of which the valve 11 l is reversed after the programme has finished, in such a way that the cylinder 107 is loaded through the pipe 109 and thus displaces the clamping carriage 103 back to its starting position. The drive is switched on by a signal being triggered by the bending tools of the bending machine 101 after their return to their starting position, with the signal being given on the time meter as shown schematically.

In an alternative embodiment also represented in FIG. 6 the clamping carriage is equipped with a drive motor 118 connected (not shown) with an impulse generator as well as with the wheels 104. The impulses of the impulse generator are fed into an impulse meter 1 19 which is set at different impulses corresponding to the individual side-piece lengths of the required loops. The sequence programme control 117 also takes over here the sequence of switching over to the next segment. Both the sequence control 117 and the impulse meter 119 act on a switch 120 which on the one hand effects the switching on and off of the drive motor 118 and on the other hand makes possible a polarity reversal so that at the end of a bending programme the clamping carriage 103 can be returned to its starting position.

In the embodiment shown in FIG. 7, there is shown the bending machine 101 and the clamping carriage 103 which conveys the rods 102 forwardly. By means of the wheels 104, the clamping carriage runs along the rail 105. This slide is further constructed as a moving electric field which is shown schematically by the line of arrows 121 which corresponds to the reduction in the distance between the bending machine 101 and the clamping carriage 103. By switching over one arrives at the line of arrows 122 which is then effective if the starting length between the bending machine 101 and the clamping carriage 103 is to be restored. The moving field influences the movable part comprising the clamping carriage 103 and the clamped rods 102 so that a linear motor is formed.

In this latter embodiment, the moving field is divided into a plurality of excitable segments, one of which is indicated at 123. The segment of the moving field which corresponds to the loop side-piece length required, is adjusted by a setting switch 124. The setting switch 124 acts on the switching-on switch and reversing switch 125 which then switches on each time a signal comes from the bending machine 101 that the bending tools have returned to their starting position. The clamping carriage 103 then only travels as far as the moving field reaches and can, if necessary, be braked by reversing the moving field. The sequence programme control 1 17 is also provided in this arrangement in order to start off the sequence of settings set on the setting switch 124 and' after the programme has finished to reverse the switch 125 in such a way that the moving field is effective in the direction of the sequence of arrows 122.

We claim:

1. A process for the multiple bending of rods, or other elongatedelements into loops in which at least one rod is supported on an abutment and is bent by a bending tool guided on a circular path around a bolt which determines the bending radius, comprising the steps providing a first bending machine movable in the longitudinal direction of the rod, arranging a second bending machine behind the first bending machine in the direction of movement of the first bending machine, clamping one end of the rod to the first bending machine, bending said one end of the rod in the first bending machine, providing a drive for the second bending machine, activating the drive to move the second bending machine so that the straight-line distance between the bending tool of the second machine and the clamped end is reduced by the length of the loop side piece required for the next single bend, clamping the other end of the rod to the second bending machine, bending said other end of the rod in the second bending machine, gradually reducing the interval between the bending machines by intervals corresponding to the bending angle side-pieces lengths, and effecting successive bends on the machines.

2. The process as claimed in claim 1, including switching off the drive by a switch-off device controlling by a signal responding to adjustable values corresponding to the required length of the loop side-piece, and switching on the drive automatically after each individual bend.

3. The process as claimed in claim 1, including reversing the drive after the last bend of a loop and maintaining the drive until the distance taking on the next rod to be bent is reached between the bending tool and a clamped position.

4. The process as claimed in claim 1 including applying a braking force in the last part of the interval between the bending tool and the clamped position.

5. The process as claimed in claim 1 including cutting the rod after the operation of the first bending machine to its required total length behind the second bending machine and prior to the second bending machine making its bends.

6. The process as claimed in claim 1 including aligning a plurality of rods located on a horizontal bearing bed by the first bending machine prior to being clamped, and guiding the bending tools on vertical circular paths.

7. The process as claimed in claim 1 including effecting several bends on each of the two bending machines.

8. A bending machine for the multiple bending of rods, or other elongated elements into loops, comprising a first bending machine movable in the longitudinal direction of the rod, said bending machine having bending tools and a clamping element, a second bending machine arranged behind the first bending machine in the direction of movement of the first bending machine, said second bending machine having bending tools and a clamping element, a drive for the second bending machine so that the straight-line distance between the bending tool of the second machine and the clamped end of the rod is reduced by the length of the loop side piece required for the next single bend, means for switching-off the drive by a switch-off device for the duration of a bending operation and switching on the drive by a signal triggered by the bending machine after the bending tools have returned to their starting position.

9. The bending machine as claimed in claim 8 in which the drive includes a hydraulic working cylinder piston unit operably connected to the second bending machine and a fixed point, and said cylinder piston unit being loaded with a fluid of constant viscosity and of a pressure kept constant for periods settable in advance.

10. The bending machine as claimed in claim 8 in which the second bending machine is provided with an impulse generation which rotates along its path, a meter which can be set at a predetermined number of impulses on which the impulses of the generator are added, and a switch actuated by the meter for cutting off the drive when such number is reached.

11. The bending machine as claimed in claim 8 in which the second bending machine has associated therewith inpulse transmitters adjustable to different values and which switch off the drive.

12. The bending machine as claimed in claim 8 in which the second bending machine is provided with a moving electric field defining a linear motor with such machine and which is switched but for the time required to provide a predetermined loop side-piece length.

13. The bending machine as claimed in claim 12 in which the moving field includes a plurality of excitable segments, the segment corresponding to a predetermined loop side-piece length being excited by a switching on of current before an individual bend.

14. The bending machine as claimed in claim 8 including a sequence programme control for switching on the drive, said control switching on the drive when the bending tool returns for the next loop side-piece length, and reversing the drive direction after the last bend.

15. The bending machine as claimed in claim 8 including a bearing bed for a plurality of rods extending in the direction of the bed, and rails extending from the tachable and guides, with the width of the bearing bed corresponding to the disc interval.

18. The bending machine as claimed in claim 8 including adjustable stops to determine the range of movement of the second bending machine.

19. The bending machine as claimed in claim 16 including two stops between which the rod cutter can be adjusted in a longitudinal direction.

Patent No. 3803893 Dated April 16, 1974 mventofls) Paul Carl Peddinghaus, et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

{30} Foreign Priority Document German No. P20 40 689.7 August 17, 1970 German'No. P21 08 937.2 February 25, 1971 Signed and sealed this 8th day of October 1974.,

(SEAL) Attest:

MCCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PC1-1050 (IO-69) gc c 03745-po9 n u. s. GOVERNMENT PRINTING orrlcz mun 0-ses-Ju. 

1. A process for the multiple bending of rods, or other elongated elements into loops in which at least one rod is supported on an abutment and is bent by a bending tool guided on a circular path around a bolt which determines the bending radius, comprising the steps providing a first bending machine movable in the longitudinal direction of the rod, arranging a second bending machine behind the first bending machine in the direction of movement of the first bending machine, clamping one end of the rod to the first bending machine, bending said one end of the rod in the first bending machine, providing a drive for the second bending machine, activating the drive to move the second bending machine so that the straight-line distance between the bending tool of the second machine and the clamped end is reduced by the length of the loop side piece required for the next single bend, clamping the other end of the rod to the second bending machine, bending said other end of the rod in tHe second bending machine, gradually reducing the interval between the bending machines by intervals corresponding to the bending angle side-pieces lengths, and effecting successive bends on the machines.
 2. The process as claimed in claim 1, including switching off the drive by a switch-off device controlling by a signal responding to adjustable values corresponding to the required length of the loop side-piece, and switching on the drive automatically after each individual bend.
 3. The process as claimed in claim 1, including reversing the drive after the last bend of a loop and maintaining the drive until the distance taking on the next rod to be bent is reached between the bending tool and a clamped position.
 4. The process as claimed in claim 1 including applying a braking force in the last part of the interval between the bending tool and the clamped position.
 5. The process as claimed in claim 1 including cutting the rod after the operation of the first bending machine to its required total length behind the second bending machine and prior to the second bending machine making its bends.
 6. The process as claimed in claim 1 including aligning a plurality of rods located on a horizontal bearing bed by the first bending machine prior to being clamped, and guiding the bending tools on vertical circular paths.
 7. The process as claimed in claim 1 including effecting several bends on each of the two bending machines.
 8. A bending machine for the multiple bending of rods, or other elongated elements into loops, comprising a first bending machine movable in the longitudinal direction of the rod, said bending machine having bending tools and a clamping element, a second bending machine arranged behind the first bending machine in the direction of movement of the first bending machine, said second bending machine having bending tools and a clamping element, a drive for the second bending machine so that the straight-line distance between the bending tool of the second machine and the clamped end of the rod is reduced by the length of the loop side piece required for the next single bend, means for switching-off the drive by a switch-off device for the duration of a bending operation and switching on the drive by a signal triggered by the bending machine after the bending tools have returned to their starting position.
 9. The bending machine as claimed in claim 8 in which the drive includes a hydraulic working cylinder piston unit operably connected to the second bending machine and a fixed point, and said cylinder piston unit being loaded with a fluid of constant viscosity and of a pressure kept constant for periods settable in advance.
 10. The bending machine as claimed in claim 8 in which the second bending machine is provided with an impulse generation which rotates along its path, a meter which can be set at a predetermined number of impulses on which the impulses of the generator are added, and a switch actuated by the meter for cutting off the drive when such number is reached.
 11. The bending machine as claimed in claim 8 in which the second bending machine has associated therewith inpulse transmitters adjustable to different values and which switch off the drive.
 12. The bending machine as claimed in claim 8 in which the second bending machine is provided with a moving electric field defining a linear motor with such machine and which is switched but for the time required to provide a predetermined loop side-piece length.
 13. The bending machine as claimed in claim 12 in which the moving field includes a plurality of excitable segments, the segment corresponding to a predetermined loop side-piece length being excited by a switching on of current before an individual bend.
 14. The bending machine as claimed in claim 8 including a sequence programme control for switching on the drive, said control switching on the drive when the bending tool returns for the next loop side-piece length, and reversing the drive direction after the lasT bend.
 15. The bending machine as claimed in claim 8 including a bearing bed for a plurality of rods extending in the direction of the bed, and rails extending from the front of the bed on which the first and second bending machine move.
 16. The bending machine as claimed in claim 8 including a rod cutter arranged at the inlet of the second bending machine.
 17. The bending machine as claimed in claim 15 in which the bolts for the bending radius and the bending tools are arranged between two vertically rotating discs, one of which holds and the other of which is detachable and guides, with the width of the bearing bed corresponding to the disc interval.
 18. The bending machine as claimed in claim 8 including adjustable stops to determine the range of movement of the second bending machine.
 19. The bending machine as claimed in claim 16 including two stops between which the rod cutter can be adjusted in a longitudinal direction. 